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Author Topic: If magnetisation isn't an energy what is it?  (Read 693 times)

Offline thedoc

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If magnetisation isn't an energy what is it?
« on: 10/03/2016 10:50:01 »
John asked the Naked Scientists:
   Could you please confirm whether magnetisation is an energy? If it is a force and not an energy, what is the fundamental difference. On Radio in South Africa yesterday, Chris said that magnetisation is not an energy.
What do you think?
« Last Edit: 10/03/2016 10:50:01 by _system »


 

Offline evan_au

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Re: If magnetisation isn't an energy what is it?
« Reply #1 on: 11/03/2016 10:39:59 »
Quote from: John
If (magnetism) is a force and not an energy, what is the fundamental difference?
Magnetism is a force field, not energy.

The magnetic force field:
  • exists at every point in 3D space around a magnet
  • is a "vector": It has a magnitude (strength) and direction
  • in theory, it extends to infinity, but in practice it is hard to detect when you move far away
  • is one component of the electromagnetic field; depending on the relative motion of an observer, it may be seen as a mix of electric and magnetic fields
  • Using an electromagnet, it is possible to turn a magnetic field on and off
A force field is different from energy:
  • Energy has a magnitude (value), but no direction, ie it is a "scalar"
  • Energy can't be created or destroyed, but it can be converted from one form to another
  • In practice, we often only deal with differences in energy between two different states
  • It takes energy to move against a force - eg to make two "South" poles approach each other
  • Moving with a force releases energy - eg to let a piece of iron approach the pole of a magnet
So force and energy are different. But they are related, such as using magnetic fields in a generator to convert mechanical energy into electrical energy, or alternatively, to use a motor to convert electrical energy into mechanical energy.
See: http://en.wikipedia.org/wiki/Magnetic_field

The above describes the modern usage of these terms. Michael Faraday, one of the early experimenters with magnets and electricity in the 1800s, used the term "Force" for concepts that we today would call "Energy". Listen to "In our Time" (45 minutes, but its near the end): http://www.bbc.co.uk/programmes/b06s9rz9
« Last Edit: 12/03/2016 01:12:21 by evan_au »
 

Offline alancalverd

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Re: If magnetisation isn't an energy what is it?
« Reply #2 on: 11/03/2016 11:54:04 »
Energy is force x distance. You expend energy moving a magnetic material in a magnetic field.
 

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Re: If magnetisation isn't an energy what is it?
« Reply #2 on: 11/03/2016 11:54:04 »

 

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